Interchangeability of Single and Double Quotes in Python

In Python programming, single and double quotes are generally interchangeable for defining strings. However, this interchangeability does not extend to JSON (JavaScript Object Notation), which has strict requirements for string syntax.

JSON requires all string values to be enclosed in double quotes. Using single quotes in JSON strings is incorrect and will result in parsing errors.

Let's consider the code example provided:

import simplejson as json

s = "{'username':'dfdsfdsf'}" #1
#s = '{"username":"dfdsfdsf"}' #2
j = json.loads(s)

In line 1, the string s is enclosed in single quotes, which is incorrect for JSON. Attempting to load this string into a JSON object using json.loads() will fail with a parsing error.

In line 2, the string s is enclosed in double quotes, which is correct for JSON. This string can be successfully loaded into a JSON object using json.loads().

Conclusion

While single and double quotes are interchangeable in Python for defining strings, they are not interchangeable in JSON. JSON strings must be enclosed in double quotes for valid syntax.